Telephone-exchange system.



E. E. CLEMENT.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED DEG. 23. 1905. R F WIQ Patented Aug.11,191

2 SHEETS-SHEET l.

E. E. CLEMENT.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED 1320.23, 1905.

L1 07, 142. v Patented Aug. 11, 1914 2 SHEETS-SHEET 2.

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. N v b T) 4 UNITED- STATES PATENT OFFICE.

EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOB, BY MESNE ASSIGNMENTS, TO FREDERICK C. STEVENS, OI ATTICA, NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented Aug. 11, 1914.

Application filed. December 23, 1905. Serial N 0. 293,148.

To all whom it may concern:

Be it known that I, EDWARD E. CLEMENT, a citizen of the United States, residing at Washington, in the Districtof Columbia, have invented certain new and useful Improvements in Telephone 'EXchange Systems, of which the following is a specification, reference being had therein to the accompanying drawings.

My invention relates to telephone exchange systems, and has for its object the provision of semi-autmnatic apparatus and circuits for the interconnection of lines,

whereby the efficiency of a system may be increased while the cost of its installation and operation may be decreased.

According to the present invention the subscribers lines do not terminate on springjacks, but upon contacts in circular rows or banks of what I shall call primary selector switches. Each of these switches is connected to a spring-jack, and as I may have one switch for every ten lines, the numberof answering'jacks is thus much less than has heretofore been possible. The operator in answering the call does not communicate with the subscriber, but merely selects an idle plug and inserts it in the jack which has been temporarily apprdpriated by the calling line. Each plug forms a single cord terminal of a trunk line leading to a first selector automatic switch, which has associated with itsecond selector and connector switches, so that when th subscriber is once given access to a set of witches, he can at once proceed 'as usual inautofnatic systems to connect himself with the wanted line.

My invention is illustrated in the accom panying drawings, in whioh-' Figure l is a diagram of a subscribers station and line, together with the cooperate ing apparatus and circuits on the manual or answering switchboard. Fig. 1 is a top plan view of the switching apparatus on the answering switchboard. Fig. 2 i a similar diagram of the trunks or automatic selector and connector switches.

Referring to Fig. 1. the subscribers station A is provided with apparatus usual in common battery systems. consisting. of the transmitter T, receiver R, hook H, condenser C and ringer Q. In addition I provide the low-wound signal magnet (3. controlling the target. which announces the answer to the call and the key K for breaking and making the circuit, both being in series with the talking set. The line-wires l and 2 pass to the contacts n and m of the cut-off relay N and thence normally to the wires 5 and 6, leading respectively to the line relay M and to ground. The relay M is connected on the other side by the wire 7 to battery B, which preferably supplies current for all purposes. The local circuit 10 controlled by the line relay M passe through the open contacts of said relay to the battery wire 7 on the one side, and to a bank contactqp individually associated with the line 12 in the primary selector switch P. The connection of wire 10 to the bank contacts may be through a switchby which it can be shifted to any one of several primary selectors P at will, in this way distributing or shifting the load according to the conditions under which the several switches are working. When the cut-off relay N is energized it disconnects the contacts n, n, from the line-relay and ground and connects them to the wires 3 and 4 leading to the talking contacts 72- in the primary selector banks. The pair of talking contacts 77, associated with eachline. bear a fixed relation to the test contact 79 in each switch.

In the selector switch P the shaft P is constantly revolving, and I use a revolving arm having a solenoid with a movable core, clutched to the shaft by the inner end of the core 7) engaging a notch 79 and the outer sion of openings in a stop or jack ring."

This ring p is concentric with the shaft and has its openings respectively opposite corresponding group of line and trunk contact springs 72, 79*, p. The springs-723p" are preferably integral throughout the circle but cut in combs with one pair of individual members opposite each pair of line-contacts 7). The solenoid has two windings S and 0 one of which controls the solenoid when a busy contact is found and the other controls and holds up the solenoid after the operator inserts the answering plug. In other words, as soon asthe wiper 7) comes upon a chargedor busy contact the winding S takes current and pulls in the solenoid core 7) loosing the: arm from the shaft and simultaneously projectingits forward insulated end through the jack ring 7; between the springs 79, [7, thereby pressing them a manual system. The relays S and N get current and S pulls up, whereupon the winding 0 gets current through the arm p" and the ring p and keeps the solenoid core pulled in. After the plug is inserted by the operator the relay BI is disconnected through the pulling up of the armature n of the cut-ofi' relay N and the test contact is free from battery so that no other solenoid with its contacts sweeping over this particular test contact would stop.

The solenoids D and D, controlled by the relays, both respond to the makes and breaks in the subscribers line while impulses are being sent to operate the automatic switches. The solenoid D holds up its core d so long as the impulses are coming in, but during the interval between each group or set of impulses the core (Z drops and sends a rotary impulse over one side of the trunk to the automatic switches. The solenoid D has its core (Z drawn up during the sending of the impulses and throughout the time the line is in use. At the end of such a time when the calling subscriber hangs up the core (1 drops and connects battery simultaneously .to both sides of the trunk, thereby releasing the various switches.

Having thus described the essential features of the apparatus wherein my invention particularly resides, I will now pass to a set of automatic selector switches with which it is intended to work conveniently, translating mere makes and breaks in the metallic circuit of the line into whatever impulses, over whatever branches, are required. These switches are shown diagrammatically in Fig. 2, being designated respectively by the letters F, F, F and are of the type shown in Letters Patent No. 815,176 and No. 815,321, granted March 13, 1906, to Keith andErickson. It is unnecessary for me to describe their mechanical connections here in, as they-are well understood by all those skilled in the art and the diagram of Fig. 2 will, therefore, besufiicient. The wires 21 and 22 which are broken at the right-hand side of Fig. 1, commence again at the lefthand side of Fig. 2 and pass to switch-arms 47 and 48, which normally rest upon contacts forming terminals of the wires 40 and 42, leading respectively to the relay magnets V and R, (which are called the vertical and rotary relays respectively) of the first selector switch F. Impulses coming over the wire 21, when .the switch is normal, afit'ect the relay V, passing through its windings to ground, while impulses going over the wire 22 afi'ect the relay R, passing through its windings to ground.

The switch F comprises a rotary spindle f, carrying insulated contact wipers w, 'w which are adapted to sweep over the set of contacts w and w constituting the terminals of trunk conductors 210 and 220 passing to second selector switches. The spindle f also carries an insulated test and releases wiper w, which sweeps over a set of contacts 10 corresponding to the contacts of the talking circuits w and w but forming the terminals of test and release circuits 60 for the second selector switches. The vertical relay V controls a magnet V called the vertical magnet, which is provided with a ratchet mechanism to step the spindle f up to the desired row of contacts w, w, w", these contacts being arranged in horizontal rows of ten each. The rotary relay R controls what is called the rotary magnet 11, which is fitted with a ratchet mechanism by which it can turn the spindle f, one step at a time, making its wipers rest upon one set of contacts after another in the respective rows selected. The magnet R is automatic in its'operation, that is to say it carries an insulating Wedge on its armature, shown at 7", which acts to make and break its own circuit as it vibrates. The armature also carries a projecting lug or stud. N, which in operation impinges against the armature z of the magnet T whose function will appear in the statement of operation.

U is the release magnet, equipped with an armature lei er, which upon being attracted will lift the retaining pawls off the ratchets of the spindle f, permitting the latter to be turned back to Zero and dropped to its normal position by a suitable spring.

T is the test and release relay, counected on the one side to the switch-arm 4S) and on the other side by wire 50 to the wiper w" In testing, the arm all) is on the middle contact, connecting the relay T back through wire 52 to the spring-contact r of the rotary relay R, which at the moment of testing is energized so as to render the relay T at that moment active.

The switch-arms LG, 4?, l8 and 49 are mounted as a unit and moved together, one step at a time, being all set back into the position shown in the drawing when the magnet U restores the switch to its zero or inactive position, and being thence released step by step by means of an escapcment carried by the armature t of the relay T The second selector switch F, and its circuits, are identical in all essential particulars with the first selector and its circuits. The vertical and rotary relays in this switch are marked V and R the vertical and rotary magnets are marked V and R, the private or controlling relay is T the test and release relay is T. and the release magnet is U'. The switch wipers are marked w, w", w, while the trunk terminals for the connector rou ps are marked w, w. and 10 The circuits bear the same numbers as their corresponding wires in the first selector, each with a naught added. Thus, the trunk-wires are 210 and 220, the side switcharms are 460,170, 480 and 190, etc.

It will be observed that ,the vertical and rotary relays and magnets are cut off in the last step of the side switch-arms heretofore described, leaving a clean talking circuit. In the connector switch F to which we now come, this is not so. The vertical and rotary relays V and R are both intended to work the switch spindle'step by step, and serve during connection to afford control over all the switches in the series, working through the back release wires and the relays T, T, etc. From its multiples in the banks of the second selector switches, the wire 61 comes into the connector switch and terminates at a condenser C, while the wire 62 terminates at a similar condenser. From 61 'a branch 63 extends to the relay V", which is grounded on the other side. From 62 a branch 64 extends to the relay R, which is grounded likewise on the other side, both these branches being permanent. The vertical relay V controls a local circuit 78, passing from the spring 42 to a pair of contacts on the relay T to the switch-arm 67. Remembering that the arms 67, 68, 69 and 70 all move together as controleld by the escapenient of the magnet T, the normal position of arm 67 puts the wire 78 into connection with the wire 80, thence to the vertical magnet V,

. which raises the spindle f step by step to 'ing included in the two sides 65 and 66 select the desired row of line-contacts; and this magnet is connected to battery by the wire 7 4. lVith the switch-arm 67 in the second position, the wire 78 is put into connec-' tion with the wire 7 9 and thence with the rotary magnet i fitted to turn the spindle f step by step, not after the fashion of the selector rotary magnets, R, R but only as energized for each step separately. Thus, the spindle may be turned around to a particular contact in the selected row. With the switch-arm 67 in its ;third position the wire 78 is connected to the wire 81 and so to the ringing relay Z, which controls the contacts 5,12 2 and 2 these contacts beof the talking circuit wires, terminating on the switch-arms 6S and 69, open during selection, but at the last stage, when the subscriber wanted is actually connected, closed to the wires 71 and 72 leading to the talking circuit wipers i r and 2o". \Vhen the magnet Z is energized it works its contacts just as an ordinary manual ringing key does, breaking the conductors 65 and 66, and connecting the forward end to the generator G.

i is the release and test magnet, X, X are bridged battery or retardation coils in the battery supply circuit to the called line. The functions of these and other parts will appear further from the statement of opera tion. It will now be possible to comprehend the operation of my invention as embodied in the apparatus illustrated in Figs. 1 and, 2.

I have not shown the substation and line of the subscriber to be called, but these are supposed to be the same as the substation A and line 1-2. live will assume the subscriber A to be calling. He takes his receiver from the hook, closing the line-circuit through his talking set as follows: B, T, M, 5, n, 1,.K, switch-hook, talking set, Q, 2, n, 6 and ground back tobattery. The relay M becoming energized pulls up its armature and closes a circuit from battery to the cont-acts p in the primary selector banks, as follows: B, 7, 8, 9, 10, p The contacts p thus having their potentials raised, when any one of them is touched by the wiper p of a primary selector switch in its revolution, the circuit through the winding S of thesolenoid is completed to ground. The solenoid thereupon pulls up its core and the insulated portion P entersthe jack springs p ,and p ,making connection with the line springs As soon as this action takes place the trunk-wires 15 and 16 are connected respectively to the wires 3 and 4, which places the relay S in series with the cut-off relay N by the following path: battery B, 110, S 104, j, j, 16, 2) y), 4, N to ground. The relay N becoming energized disconnects the line relay M and connects the line wires 1 and 2 to the trunlewires 15 and '16, respectively. The relay M being disconnected frees the test contact 1) from battery and the circuit of the winding S of the solenoid isopened, but the circuit of the winding is completed by the following path: battery B, 110, 102, the contacts of the relay S. since this relay becomes energized as soon as the trunk is connected to-the line wires, wire 39, 72, 0 to ground, thus keeping the solenoid energized and the core with its insulated end P inserted in the jack. The relay S be coming energized closes the circuit of the lamp mby the following path: battery B, 110, 101, m to ground. The operator notices the line lamp glowing and inserts the plug P in the jack J in the usual manner. This in.- sertion disconnects the relays S and S from the trunk wires 15, 16, respectively, by

breaking the contacts j, 7' and j, j. The

winding 0 of the solenoid is now supplied with battery by the following path: battery B, 7, contacts 8 of the relay 9 which is now energized, having its winding in series with the cut-off relay N, 28, 7) j'-, 89, 2, 0 to ground.

It will be observed upon tracing the foregoing circuits that when the operator inserts the plug and puts battery through the corductors 15 and 16 to line this battery is reversed in direction from that normally on the line. Hence the polarized magnet Q at the substation will reverse its armature from the position shown, raising the target and indicating to the subscriber that his call is answered and switches placed at his command. He then proceeds to manipulate the key K so as to connect himself with the line wanted.

I preferably provide a sufficient number of primary selectors for each group of lines so that each line may have at least ten multiple-contacts on each of the sets 29 [7. These contacts are eitheridentical in every switch as to their angular position (in which case the wipers p", p must be displaced one step in each succeeding switch), or the contacts of the same line may be displaced and set'in each succeeding switch, and the wipers in all the switches of a set may then have the same angular position with relation to the shaft p.

Assume that subscriber A desires to converse with subscriber No. 2468. He first taps the key K twice each time breaking the circuit and quickly making it again. He then permits a short interval to elapse. The first short break causes the relay S in Fig. 1 to let go its armature, whereby for a brief instance current is transmitted over the following circuit: B, 7, 30, s", 29, 28, s", 31, 32, D, 23, and ground. At the same time current is sent over-a second branch from the wire 31 by way of 33, (2", d and 35 to the wire 21. This is the vertical side of line, and the pulse of current proceeds to the first selector switch in Fig. 2, which will be referred to presently. -That portion of the current which reaches solenoid D causes it to pull up quickly, closing the springs (Z, d together in passing, but it should be noted that while this closes the circuit 37, 38, it does not produce any effect because battery is disconnected from the wire 26 and hence from the wire 24, because at the instant the solenoid pulls up the armature s of the relay S is back. It is true that this also takes'current off the solenoid D, but the break is very short, and while either solenoid will pull up on a momentary impulse, neitherof them will fall back far enough to perform any work, except on a long change in current. Hence the solenoid D is unaffected by the short number impulses coming over the line. Both solenoids now have their cores attracted, and so lon as the subscriber is sending short brea s, thereby oscillating the armature a back and forth, just so long will both solenoids hold up. Each closure of the armature 8 on its back contact, sends a pulse of current to the wire 21 by the path already traced, so that in calling 2468 two breaks being made, two pulses of currents will be sent, and then as the subscriber leaves his line circuit closed, the relay S will continue to hold up, and

the solenoid D. being deprived of current for a considerable period, will let its core retract far enough to close the springs d, (1',

and send a single pulse of current to the wire 22 by the following path: B, 7 ,-30, s 29, 2s, 8 2c, 24, 38, d, d, 37 and 22. The wire 22 is the so-called rotary wire of the first'selector switch in Fig. 2. Thus two short breaks produced in the metallic circuit have been translated into two current impulses on the vertical side 21, and one impulse following the group, on the rotary side 22. In a similar manner the next number, 4, is transmitted by making four short breaks at the key K, which are translated into four impulses on the vertical side 21, followed by one impulse on the rotary side 22. Each succeeding group of short breaks is translated'in the same way, all that the subscriber has to do to send the number have mentioned'being to tap the key twice, then four times, then six times, and finally eight times, leaving a reasonable interval between the groups. Here the peculiar features of my invention end.

So far as the present application is concerned, any desired form and arrangement of switches and circuits may be adopted, and it will be found that my solenoids and relay scheme of Fig. 1 will enable any standard switches to be worked merely by the subscriber making and breaking the metallic circuit. I emphasize this because it is exceedingly important for two reasons: In the first place it is undesirable and is now considered bad practice to have any grounds on the lines if they can be avoided: and in the second place I am enabled to apply my present invention to existing common battery systems having metallic circuits by merely supplying a separate box or casing with the circuit breaker K of any desired type and the signal device Q. To connect this for operation requires merely that its binding-posts shall be interpolated in the talking circuit.

I have shown-how by tapping his key the subscriber sends successive groups of impulses over the wire 21, and a single impulse at the end of each group over wire 22. This is all it is necessary to assume or to remember in order to understand Fig. 2. The first two impulses come over the wire 21 and cause the relay V to pull up twice, each time closing the following circuit: battery B, 7, 55, 57, V, 56, contacts'of magnet T, 59, '0, g, 60, and ground back to battery. This causes the magnet V"to step up the spindle f two steps, so as to bring the contact wipers w, w and w opposite the second rows of contacts. In these rows are the terminals of trunks 210, 220 and test contacts 10 of trunk conductor (30, leading to ten second selector switches of the orderof 2000. Following the group of two impulses over wire 21. comes the single impulse from wire 22. This energizes rotary magnet R, which pulls up and closes the following cirfor their last step.

cuit: battery B, 7, 55, T, 1', g, 60 and ground back to battery. The magnet T thereupon pulls up, breaking the circuit 5659 of the vertical magnet V, and making the first movement of the escapement so that upon the retraction of the armature .t, the side switch arms 46, 47, 48 and 49 are permittedto move one step, whereupon the following circuit is immediately closed for the rotary magnet R: battery B, 7, 55, 57, R, 58, 46, 43 and ground back to battery. The rotary magnet R thereupon pulls up, its stud, 1", breaks the circuit and it lets go, the stud closes the circuit and it pulls up again, and so on with the following results: Each time the armature of the rotary magnet pulls up, it steps around the spindle f one step, and causes each wiper to pass from one contact to the next, making contact with the succeeding one, however, before it leaves the preceding one. the armature of the rotary relay, the'fhrmature t of the relay T is kicked ripby the stud 1' but released when the wipers come on a fresh contact. That is to say, on the forward stroke the armature t is forced to take the first step toward removing the escapement to release the side switch-arms Now as the wiper 10 passes over the successive contaets w of the different trunks all leading to second selectors numbered 2000, it is hunting for an idle one, and the idea is to have the side switch move a second step when an idle trunk is found. Each contact that is busy has a ground onit, as will presently appear. Hence, if in its first movement the wiper w finds such a grounded contact, it will at once close the following circuit: battery B, 7, 55,

", 2, -49, T, 50, 10, w and ground back to battery. As stated, on the first part of the stroke the armature t is'mechanically held up. Current flowing in the circuit I have traced holds it up in the second part of the stroke of the rotary armature, so that after the armature t is once kicked u it stays up, held alternately by the stun? r" and by its own magnet T, until an idle or ungrounded contact w is reached. When this happens the armature t falls back, and its escapement permits the four switches 46, 47, 48 and .49 to take their last step. Switch 46 cuts 011' the rotary magnet and stops the machine i'nstantly..- 47 and 48 cut off the vertical and rotary relays V and R, and complete the talking circuit: 21'44, 22-45. 49 cuts off the magnet T.,'and closes thecircuit of magnet T through wire 51 to ground, thus put-ting a ground on the wiper 10 and all the multiples w 'of the contact on which it rests, rendering the trunk busy, so that no other switch can get in. It is proper to say that the' magnet T will not work on thetest current through any relay T. \Ve now have at the endof- At each movement of the first group of two impulses, the wires 21 and 22 extended respectively as follows: 21, 47, 44, w, w, 210, 470, V and ground; 22, 48, 45, 20 w", 220, 480, R and ground' In other words, the circuit has been extended into the second selector switch F and the relays V and B have been substituted for those of the firstselector. \Ve now have the second group of four impulsescoming over the combined wires 21 and 2l0, followed by a single impulse over the combined wires 22 and 220. The operation of the relays and other parts is precisely the same in this switch as it was in the firstselector, the only differences being in matters of release, etc., which will be touched upon later. The net result of the operation of this switch is to pick out an-idle connector switch F and prolong the circuits as follows: 21- 21061; and 22--220-62. The relays V R of the second selector are cut off, and the relays V R are substituted therefor, their connections 63 and 64 being permanent, for these two relays are used in releasing the set of.switches as well as in selecting.

The subscriber now sends six impulses to relay V each of which causes the same to pull up, operating the vertical magnet V over the following circuit: battery, 7, 74, V 80, 67, 78, contacts of relay T m, 60 and ground back to battery. The number of the wanted line is 68, so that the six impulses working in this way through magnet V step up the spindle f to the sixth row of line-contacts. single impulse over the wire 62 to the rotary relay R which pulls up and closes the following circuit-z battery B, 7, 75, 77, T 1', 60 and ground back to battery. The magnet T pulls up and then lets go, it being observed that there is no rotary kicker to hold it up in this case. The side-switcharms 67, 68, 69 and 70 are therefore stepped around promptly one step. Vertical magnet V is thereby cut out and rotary magnet R cut in, but this magnet has no vibrator, being constructed to turn the switch spindle only one step at a time. The subscriber now sends his final number 8 over the wire 61, and the same relay V responds, each time closing" the following circuit: battery The subscriber then sends a.

B, 7, 74,11, 79,67, 78, contacts of relay T v,

60 and ground back to battery. The spindle is therefore stepped around until the wipers 10 ,40 rest upon the contacts belonging to line 68 in that hundred. A single impulse now comes over the rotary side of line, and

pulls up the relay R, which closes the following circuit, for testing to ascertain if :lowing circuit: batter B, 7, 75, release relay U 76, contacts of re ay T '82, 70 (this be ing on its second point), w", and to the tip.

side of the line being tested. 'Now, if the line wanted, is already connected either through a connector switch, such as shown in Fig. 2, or through a primary selector switch, such as shown in Fig. 1, there will be a ground on the tip side, otherwise not.

In the first case, the ground will be throughwanted is not busy, the momentary impulse over the rotary side ceases, the relays R", T

let. go, and the side switches go the last step, cutting off the working magnets R, V entirely, substituting the ringing relay Z through the wire 81 and the arm 67, and completing the circuit of wires 65 and 66 through 71- and 72 to the line wanted. In order to ring the vanted subscriber, the next thing is to energize the relay Z, which is ordinarily done by simply breaking the circuit at the calling subscribers station by means of a push-button. In the present system we cannot do this because a prolonged break would deenergize the solenoid D, and would release all the switches. So I do not provide any special ringing button, but after the line wanted is selected, a succession of taps on the key K is produced by the calling subscriber, and these energize the relay Z, by energizing the relay V. I preferably make the relay Z a solenoid like those shown in Fig. 1, so that the succession of short closures will hold its core up as long as they continue. The energization of this relay opens the springs z, z, 2 2*, and closes 2 on 2 and a on 2 thus connecting the ringing generator G across the wipers w 'w". When the called subscriber answers, he derives current for his transmitter from the main battery through the bridging coils X and X.

When the subscribers have finished talking, or in the event that the caller finds the wanted one busy, the receivers are hung up, the metallic circuits being thus opened at the substations. Referring to Fig. 1, it will be observed that this opening at's'ubstation A lets go the relay S, which cuts off the solenoid D, whose cored? drops to its nor- -mal position shown in the drawing. The

Springs 4, (Z and J? therefore come together, and battery is put on both trunk-. wires 21 and'22, by the following path: B, 7, 30, 8 29, 34, d, d,;and 03, through wires 36 and 35, Referring to Fig. 2, these simultaneous impulses over both trunk-wires 61 and 62 energize both relays V and R at the same time, closing together the springs m: and m, and the following release circuit: battery, 7, 75, U 76, m, m, 10 10*, T, 490, ground back to battery. Magnet U releases and restores the connector switch F relay T closes the following release circuit: B, U, contacts of T, (50, w", w, 50, T, 4-9, 51 and ground back to battery. Magnet U thereupon releases and restores the switch F, and relay T closes the following release circuit: B, 7, 55, U, 51, contacts of '1, ground back to battery. Magnet U thereupon restores the switch F. All the automatic switches are therefore restored he de energization of the relay S also closes the circuit of the supervisory lamp 3, causing it to glow. The operator perceiving this disconnect signal withdraws the plug 1" from the jack J, opening the circuit of the winding 0 allowing the plunger or core to spring back and the insulated portion P to leave the jack, whereupon the solenoid begins to rotate in the usual manner and the subscriber is free to make another call at any time.

Having thus described my invention, what I claim and desire to secure by Letters Patent is 1. In a telephone exchange system a plurality of subscribers lines, a number of answering jacks less than the number of lines, an automatic switch adapted to connect a calling line with an idle answering jack, an answering plug adapted to cooperate with said jack, an automatic switch for selecting and connecting with a wanted line, a trunk directly connected to and terminating in said plug at one end and similarly connected to and terminating in said automatic switch at the other, said automatic selector switch being fixedly and permanently connected with said answering plug, and means to actuate said switch to select a wanted line, substantially as described.

2. In a telephone exchange system a plurality of subscribers" lines, a number of answering jacks less than the number of lines, an automatic switch adapted to connect a calling line with an idle answering jack, a cord-circuit terminating at one end in an answering plug, and at the other end in an automatic selector switch, and means to actuate said switch to select a wanted line, said means being controlled by the calling subscribers, substantially as described.

3. In a telephone exchange system a plurality of line-circuits, and means for interconnecting them comprising the following instrumentalities: primary switching mechanism for answering calls, an answering jack connected thereby to a calling line, a calling signal associated with said jack and becoming energized when the same is so connected, an answering plug adapted to connect the jack with a cord-circuit and by its 7 insertion in the jack to restore or retire the call signal, a supervisory signal associated with said answering plug, an automatic selector switch for selecting and connecting with a wanted line, a trunk directlyconnected to and terminating in said plug at one end and similarly connected to and terminating in said automatic switch at the other, and means to actuate said selector switch, substantially as described.

4. In a telephone exchange system, a plurality of line-circuits, and means for interconnecting them comprising the following instrumentalities: primary switching mechanism for answering calls, an answeringjack connected thereby to a calling line, a call signal associated with said jack and becoming energized when the same is so connected, an answering plug adapted to connect the jack with a cord-circuit and by its insertion in the jack to restore or retire the call signal, a supervisory signal associated with said answering plug, an automatic selector switch for selecting and connecting with a wanted line, a trunk directly connected to and terminating in said plug at one end and similarly connected to and terminating in said automatic switch at the other, means to ac-' tuate the selector switch and means for restoring or releasing the same, substantially as described.

5. In a telephone exchange system a plurality of line-circuits, and means for interconnecting them comprising the following instrumentalities: primary switching mechanism for answerin calls, an answering jack connected there 'y to a calling line, a call signal associated with said jack and be 'coming energized when the same is so con nected, an answering plug adapted to connect the jack with a cord-circuit and by its insertion in the jack to restore or retire the call signal, a supervisory signal associated with said answering plug, an automatic selector switch adapted to connect the cord-' circuits with a wanted line, means at the subscribers station for actuating the selector switch, and means controlled by the subscriber for releasing or restoring the same, substantially as described.

6. In a telephone exchange system a plurality of line-circuits and means for interconnecting them, comprising the following instrumentalities: a number of answering? jacks less than the number of lines, an automatic switching device for connecting a calling line with an idle answering-jack, a cord-circuit terminating at one end in an answering plug to cooperate with said jacks, and at the other end in arsystem of automatic selector and connector switches for selecting wanted lines, together with controlling means for said, automatic .switch-.

ing device between the lines, and answeringjack, initially controlled by the calling subscriber, but controlled during connection through the jack and plug and thence through the cord-circuit, whereb a calling line will remain connected with 1ts answering-jack until the answering-plug is finally withdrawn therefrom, substantially as described.

7. In a telephone exchange systein a plurality of line-circuits, each having a cut-off relay, a line-signal relay, and answering and connecting terminals, the former in the banks of contacts of primary selectorswitching means, andthe latter in the banks of automatic selector switches, a number of answering-jacks less than the number of lines, each ,jackconnected to a rimary switching device, and adapted there y to be connected to calling lines, calling signals associated with the answering jacks, means associated with the line-relays to initially control the primary switching devices, means to energize each calling signal when a line is connected to its associated jack, answering plugs having cordcircuits connected to the automatic selector switches, means associated with each answering-plug to control the primary switching device and maintain it in connection with the calling'line while "the plug is in the jack, means operated by the plug to restore the calling signal, and'a supervisory. signal associated with the plug circuit, substantially as described.

8. In a telephone exchange system a plu,- rality of line-circuits, each having a cut-off relay, a line-signal relay, and answering and connecting terminals, the former in the banks of contacts of primary selector-switching means,.and the latter in the banks of automatic selector switches, a number of answering-jacks less than the number of lines, each contact connected to a primary switching device, and adapted thereby to be connected to calling lines, calling signals associated with the answering-jacks, means associated with the line-relays initially controlling the primary switching devices, means to energize each calling signal when a line is connected to its associated jack, an-l swerin plugs'lhaving cord-circuits connected to t e automatic selector switches, means associated with each answering plug to controlfthe primary switching device and maintain it in connection with the calling line while the plug is in the jack, means operated by the plug to restore the calling signal, and

a supervisory signal associated with the plug circuit, together with means controlled y a calling subscriber for actuating and releasing the automatic selector switches, substantially as'described.

.9. In a telephone exchange system, a plurality of subscribers; lines and substations rovided with sending device's, answering 1acks less in number than the number of linesfand means including terminal plugs and automatic switches controlled by said rality of subscribers lines and substations provided with sending devices, a number of answering jacks therefor less than the total number of lines, automatic switching devices adapted to connect the subscribers lines, when calling, to the answering jacks, terminal plugs and automatic switches controlled by said sending devices for effecting connection with other lines, substantially as described.

11. In a telephone exchange system, a plurality of subscribers lines and substations provided with sending devices, a number of answering jacks therefor less than the total number of lines, means to connect a calling line with an idle jack, and means including terminal plugs and automatic switches controlled by said sending devices for connecting said jack with the line wanted.

. 12. In a telephone exchange system, a plurality of subscribers lines and substations provided with sending devices, a number of answering jacks less in number than the number of lines, automatic switching devices adapted to connect each calling line with an idle jack and means including a terminal plug. and automatic switches controlled by said sending device for connecting said jack with the lines wanted, substantially as described.

13. In a telephone exchange system, a plurality of subscribers lines and substations provided with sending devices, a number of answering terminals therefor less. than the number of lines, a calling signal associated with each terminal, means to connect a calling line with an answering terminal, means thereupon becoming active to operate said signal together with automatic switches responsive to said sending devices for effecting the connection of a calling and a called line.

14. In a telephone exchange system, a plurality of subscribers lines and substations provided with sending devices, a number of answering spring jacks therefor less than the number of lines, a calling signal associated with each spring jack, means to connect a calling line with an answering jack, means thereupon becoming active to operate said signal, together with means including a, terminal plug and automatic switches controlled by said sending device, for connecting the spring jack with the wanted line, whereby the calling signal may be restored or retired, substantially as described.

15. In a telephone exchange system, a plurality of subscribers lines and substations provided with sending devices, answering jacks less in number than the number of lines, automatic means for selectively effecting connection between an answerin jack and a calling line, automatic means or effecting a connection with a wanted line, an operators manual means for effecting connection between an answering jack and the line connecting means, means for restoring said line connecting means controlled by the calling subscriber and means for restoring the said line selective means controlled by the operator.

In testimony whereof I aflix my signature in presence of two witnesses.

EDWVARD E. CLEMENT.

\Vitnesses E. EDMONS'ION, J1'., JAMES H. MARR. 

